Document aB04YoxJojE9QpQBpEBko6MvR

AMERICAN Industrial Hygiene JournalASSOCI ATIO n Volume 23 January-February, 1962 Number I TABLE OF CONTENTS Changing Objectives in Occupational Health........................................................................... Theodore Hatch 1 New Concepts and Future Trends in Toxicology.................................................................. Herbert E. Stokinger 8 Modern Concepts of Air Samplinc and Problems for the Future............................ 20 H. F. Schulte Modern Concept of Analytical Chemistry in Industrial Hygiene and Problems for the Future........................................................................................................................ J. Cholak 26 Modern Concepts of Diagnosis and Treatment in Occupational Medicine......... Mitchell R. Zavon, M.D. A Toxicologist's View of Threshold Limits......... ................................................ ...................... Henry F. Smyth, ]r., Ph.D. 30 37 Threshold Limits and Maximal Acceptable Concentrations: Their Defini tion and Interpretation, 1961................................................................................................... ......... Herbert E. Stokinger, Ph.D., Chairman, Threshold Limits Committee, American Conference of Governmental Industrial Hygienists 45 An Improved Continuous Internal-Electrolysis Analyzer for Gaseous Fluorides in Industrial Environments......................................................................................... O. H. Howard, A.B., and C. W. Weber, Ph.D. 48 Separation and Analysis of Dust in Lung Tissue.................................................................... 58 N. A. Talvitie and Lial W. Brewer In-Service Solvent Cleaning of Electric Motors.................................................................... 62 D. L. Stoddard and W. R. Wells Dust Control in the Asbestos Textile Industry.................................................................... 67 Benjamin F. Postman, M.E. Use of Statistical Methodology in EnvironmentalMonitoring................................. 75 Gerald W. Kerr Planning Ventilation for NuclearReactor Facilities........................................................... 83 Bruce J. Held A System for Exposure of Mice to an Atmosphere Containing Carbon Particles ............................................................................................................................................................. 08 Eric G. Comstock, Roger R. Rue, and J. H. Gast News of Local Sections................................................................................................................................ 91 President's Page.................................................................................................................................................... A-2 American Industrial Hygiene Association Journal, published bi-monthly by the American Industrial Hygiene Association. Dohrman H. Byers, Editor; Kenneth W. Nelson, Associate Editor; Philip Drinker, Consulting Editor. Editorial offices, 1014 Broadway, Cincinnati 2, Ohio. George D. Clayton, Publications Manager. Business office. 14125 Prevost, Detroit 27, Michigan. The subscription price is $7.50 per year in U.S.A.; $7.75 in Canada; $8.25 elsewhere. Single copies, when available, may be purchased from the business office, $1.50 per copy in U.S.A.; $1 75 elsewhere. Copyright fj) 1962. by the American Industrial Hygiene Association. Entered as second class matter at the post office at St. Paul, Minnesota. The Association reserves the right to edit all advertisements and to refuse advertising copy when it does not meet the high standards adopted by the Association. Library of Congress Catalogue No. 57-3151. Printed for the American Industrial Hygiene Association by PLAINTIFF'S THE BRUCE PUBLISHING COMPANY, SAINT PAUL 14, MINNESOTA! | EXHIBIT \SoA Dust Control in the Asbestos Textile Industry BENJAMIN F. POSTMAN, M.E. Industrial Hygiene Engineer, 69-02C 186 Lane, Fresh Meadows 65, Flushing, Long Island, New York (g Some of the sources of asbestos dust exposures in the asbestos textile industry are described. Two important and moderately involved dust control problems are dis cussed for carding units and weaving looms. Illustrations are included. Introduction physiological standpoint and usually eco nomically impracticable." IN A VERY comprehensive publication The first comprehensive medical and en Industrial Health Hazards and Occupa gineering study of the health hazards in the tional Diseases in Ohio resulting from a stateasbestos textile industry in this country was wide survey during 1914 by Dr. E. R. Hay- made in 1937. This was a cooperative study hurst, Director, Division of Occupational made by the U. S. Public Health Service and Diseases, no mention is made of any asbestos the State Board of Health and the Industrial processing operations, possibly because there Commission of North Carolina. The results may not have been any in Ohio at that time. of this project were published as Public Between October 1929 and January 1931, a Health Bulletin No. 241 entitled A Study of study was made of the potentiality of asbestos Asbestos in the Asbestos Textile Industry. as a health hazard for the Metropolitan Life Insurance Co. by Dr. A. J. Lanza, Dr. YV. J. McConnell, and J. W. Fehnel. This request came from officials representing the asbestos industry in the United States. Then followed a two-section publication by the Commonwealth of Pennsylvania. Depart Operations and Controls Asbestos as received in burlap bags, passes through a scheduled routine of operations such as preparation, carding, spinning, twist ing, brake-band and broad cloth weaving and ment of Labor and Industry, issued as Special Bulletin No. 37, October 1934, and No. 42, September 1935. This study was under the through other varied processing equipment, depending upon the final use of the products. This paper covers some of these processes. supervision of Dr. W. B. Fulton, Chief of Not much of the asbestos processing equip Industrial Hygiene. This was followed by ment is or has been designed for asbestos pro A Study of Dust Control Methods in an duction. Practically all equipment in use is Asbestos Fabricating Plant in October 1938 similar to that used for cotton and woolen by J. J. Bloomfield and R. T. Page of the goods production, with only slight or no Public Health Service. The following are modification. some of the conclusions at the end of this Figure 1 illustrates the first major operation study: "Adequate data have not yet been in asbestos processing to free the fibers from published to justify the determination of the rock--the use of a mill for crushing the threshold limits of dustiness which will pro raw stock as it is received from the mines. duce asbestosis in any definite period of time. Though not much dust seems to be dispersed In the absence of such threshold values, it is during the crushing action of the large steel not possible to determine permissible limits of rollers as they revolve about on the inside of dustiness on a medical basis. Nevertheless, the steel housing, which operation may range any appreciable decrease in the amount of from 5 to 20 minutes, considerable dust is asbestos dust will cause a decrease in the in dispersed when the stock is dumped out of cidence and severity of the resulting asbes the burlap bags and again when the crushing tosis. The elimination of all dust in an in operation is completed and the stock is either dustrial workroom is rarely necessary from a discharged to the floor, into wheeled contain- 67 68 January-February, 1962 Figure 1. Mill for crushing asbestos fiber. ers or replaced in bags by hand for subse quent processing. The particular technique involved depends upon the extent of the variations in production procedures or the extent of the mechanization which has de veloped in the industry. Little published data are available relative to operator exposure at these units, usually one or two in a plant, since there are many other processing units continuously in opera tion in the same department, so that results are usually tabulated under the heading of Preparation Department. Concentrations may vary from 2-8 million particles per cubic foot of air (mppcf). Operators are not usually stationed at these units even though the cycle of operation may be of short duration. This situation may vary depending upon stock production demands. The entire top of the steel pan may be pro vided with a mechanically exhausted en closure, complete with an opening through which a bag of stock may be emptied. Opera tors should be provided with and be required to wear approved respiratory equipment, but this is rarely done. If available, the equip ment is usually not worn. An Opener or Willower is illustrated in Figure 2. In some of the older plants crushed stock was usually dropped on the floor and actually heaved into the open feed bin of the unit--shown at the right of the unit, pro vided with exhaust. Handling was usually performed by means of a pitchfork. This hand tool created as serious a problem in the asbestos textile industry as does the shovel in the foundry industry. In many installations modern handling procedures feed the crushed stock directly to the feed bins, eliminating one serious source of asbestos dust dispersion in the Preparation Department. The beating and combing action which takes place within the machine produces a large amount of dust which is forced out of the usually loose-fitting enclosure. The pro duction of dust is severely increased when waste asbestos, recovered from cyclone sep arators which form a part of the usual dust removal system, is willowed for reclaiming purposes. This is called "fly willowing." All asbestos fibers must be mixed with cot ton before they can be spun and woven. As a rule, from 5 to 20% by weight of cotton is added to asbestos textiles produced in this country. This is due to the fact that the in dividual asbestos fibers resemble fine polished metal rods, free from any serrated surfaces. This characteristic explains the extreme dif ficulty encountered in attempting to spin a thread of pure asbestos. A certain amount of cotton fiber must be added as a binder or supporting agent for proper spinning. Mod ern textile production specifications may also include the use of synthetic fibers. The pre-mixing operation is called piling or layering and consists of placing cotton and Industrial Hygiene Journal 69 asbestos in alternate layers in a pile. In some of the older plants this is or has been done on the floor near the Picker Mixing Unit. This is an exceedingly dusty opera tion. Modern procedures have eliminated hand layering or piling and it is now done automatically by feeding both stocks on to a belt conveyor for transportation to the mixing unit. In some plants a spray of mineral oil may be automatically added to the layered stock. The Picker Mixing Unit also produced considerable asbestos dust. Modern adequate dust control has changed this. The initial dispersion resulted when the mixed stock was discharged into the feed hopper and the high speed internal cylinder and auxiliary rollers created fine dust which was forced out of the enclosure by the fan action of the equipment. In the older installations partial enclosures, little or inadequate local exhaust and pitch fork handling of stock, all added their quota to the dust exposure. These serious dust-pro ducing operating conditions have practically disappeared from the modern asbestos textile plant. The mixed stock is usually air-conveyed to storage bins before it goes to the next opera tion which is carding. Mixed stock from the storage bins is hand moved or forked to hand trucks. On arrival at the carding units, the stock is again hand moved from within the trucks to the feed hopper of the first unit of breaker card. Revamped handling proce dures in some of the modernized plants may include pneumatic conveying of the stock directly to the feed bins of the Breaker Card Unit. The carding performs two functions, provides additional mixing and arranges the fibers in parallel positions to form roving from which textile yams are produced. The twin carding units consist of a break er card and a finisher card. The stock is transferred from the rear of the first card to the rear of the second card by a so-called camelback inclined slat conveyor. Each card consists of a central large diameter cylinder and many auxiliary rollers, the surfaces of which are studded with fine steel bristles like a hair brush. These are high speed machines, which cause considerable asbestos dust dis persion. The exit mechanism of the finishing card separates the web into ribbons and by means of a transverse action of mbber-covered shafts, these ribbons are rubbed mechanically and are condensed into untwisted strands called roving. All carding units are provided with en closures, some partial and some complete, and are mechanically exhausted. Much is to be desired relative to dust control in some in stallations. There are two problems involved, containment of the fine asbestos dust created Figure 2. Fiber recovery- process using willower and vibrating screens. 70 January-February, 1962 by the action of the high speed pin-studded processing cylinder and circumferential rolls and the application of minimum exhaust to prevent the removal of stock from the cards to the dust collectors. Since the fan action of the equipment creates an internal pressure within the enclosure, any opening becomes an exit port for the dispersion of fine asbestos dust particles. In Figures 3a and 3b two types of applied Industrial Hygiene Journal 71 exhaust are illustrated, first a so-called stand ard "trade" type and the second a studied and engineered design which had proven satisfactory in one plant. The acceptance was based on the definite reduction in visible dust dispersion and a demonstrable reduction of essential stock removal from the stock being processed. There is no top central ex haust as is normally provided through the so-called "standard" card enclosure. The two partial circumferential ducts, 4x6 inches are provided with slots one-half inch wide along the lower plate of each duct. Three 4-inch diameter exhaust connections distrib uted along the top plate of each duct provide excellent exhaust distribution, Subsequent processing operations involve spinning, twisting and winding. The yam or roving is twisted or spun into threads on either mule or ring spinning frames. The spinning process is one of imparting a twist to the roving to facilitate further processing and to provide tensile strength. The twisting operation involves the twisting of several single yams to provide larger and stronger yams. Figures 4a and 4b illustrate a twisting frame and a modem spinning frame. Few of Figure 4b. A front baffle on a spinning frame effectively controls the dust. The enclosed bottom area is provided with exhaust ventilation. Figure 4a. This view of a twisting frame shows where whipping action of threads causes dispersion of the dust. these units are provided with exhaust though the present tendency is to provide such pro tection. In February 1947, a design was submitted to one plant to exhaust one spinning frame as an experiment. The idea was rejected, pos sibly because there was no such unit properly functioning in the entire industry at that time. A spinning frame is approximately 39 ft. long and production mechanism is located both along the front and rear upper longitud inal machine areas. The design contemplated blanking-off one main longitudinal section extending upwards approximately 16 inches from the floor and tw'o other auxiliary longitudinal sections each approximately 8 inches in height. There would only remain a longitudinal section ap proximately 10J4 inches in height at the rear of all spools being wound for air entrance re quirements. The spool area is the generating point of maximum dust dispersion due to the high speed whipping action of the thread as it travels down from the jack spools above. 72 January-February, 1962 Ficure 5. Broadcloth weaving loom. passing through rollers and guides until it is finally wound on the spools below. Such a design is shown in Figure 4b with one additional important feature--the pro vision of sectional partially curved baffle plates located in the area where the whipping action of the thread is most intense. These plates prevent excessive dust dispersion re sulting from the whipping action of the thread. Exhaust air is drawn across, above and below the plane of the spool area, through the longitudinal area at the rear of the spools, leading to floor openings. These openings terminate in exhaust ducts located near the ceiling of the lower floor. Commer cial designs seem to be available but no en gineering data are revealed. The final item of presentation covers cloth weaving. Little if any attention had been given to the control of dust dispersion from this operation and few plants are known to have installed adequate dust control. There seems to be a peculiar apathy in connection with the control of asbestos dust from weav ing looms possibly because there is so much exposed moving mechanism. Further, the continuous periodic stopping of the loom mechanism to repair thread breaks may be responsible for the lack of interest to house any of the moving mechanism. The unexhausted broadcloth loom is seen in Figure 5 with the large number of threads in the upper right area being fed from a portable structural steel unit called a creel. Depending upon the cloth width desired, there may be as many as 1500 threads lead ing into the cast iron heddle frames in the center of the loom. The shuttle mechanism, which whips across the front of the loom and then automatically reverses itself, is not clear ly shown. Early attempts to provide exhaust ventila tion above the area of the shuttle bar move ment were not very successful. The arrange ment may be explained as follows: 1. Vertical rectangular exhaust ducts are located at each side of the loom frame. Each upper duct section is provided with a pivot joint so that it may move forward over the shuttle path and then back to a vertical position as the woven cloth slowly moves forward to the wind-up spindle. 2. Across the area above the cloth and shuttle, where the shuttle movement de velops, is a horizontal duct section con nected to the pivot connections of the vertical side duct legs. The lower sur face of this duct is provided with a narrow slot 0.5 to 0.75 inch in width, usually tapered from the center of the loom to the elbow which connects to the vertical side legs. Some of these units were never found Industrial Hygiene Journal 73 Figure 6a. Diagram of hood enclosure for broadcloth weaving loom. Figure 6b. Front view of hood enclosure for broadcloth weaving loom showing front-opening plexiglass windows. Figure 6c. Rear view of enclosure for broad- cloth weaving loom showing catch-pan and ex hausted hopper. 74 January-February, 1962 satisfactory to provide adequate dust control special reference to control at weaving looms. due to the fact that even with moderate air It required a waiting period of eighteen entrance velocity to the slots comparatively years to finally convince one plant in the in little air was being moved, but more par dustry' to utilize this design for nine dry weav ticularly and from personal observation, the ing looms. A competitor, learning of this in prime area of dust dispersion is at the cast stallation, installed the control for five dry iron heddle frames, which move up and down weaving looms. continuously. The asbestos-cotton threads The entire enclosure may be disjointed pass through flattened steel eyelets which are from the overhead hood for complete ac- a part of steel wire units comprising the cessability. The front of the unit is provided heddle frame. The upward and downward with sectional plexiglass windows to watch movement of these frames create a chafing or for broken threads. As can be seen, the rubbing action of the threads, releasing con hinged windows may be raised, providing siderable asbestos and cotton dust not only to complete accessability to the area between the the breathing zone of the operator but to the shuttle and the heddle frame. entire production area. In some plants, fine There is provided a catch-pan and ex dust dispersion from cards and looms is char hausted hopper at the rear of the loom. acterized as "smoke." Then there is the con The minimum floor droppage of stock is evi siderable quantity of floor-droppings which dent. There is some droppage from the lower add their quota to the environmental dust center area of the loom but the loom load. This will be discussed further. mechanism prevented any collection control A second attempt, provided by the en at this area. This may be done by cutting gineering department of one plant, is a modi through the floor with a fish-tail connection fication of the first idea, except that the ex located below the floor and vertical panels haust is upwards and not downwards, the could be provided from the floor to a point slots are not continuous but are about 9 x 34 upwards, this height to be determined by the inches and the end connections are 3 inches interfering mechanism. A vacuum cleaner in diameter. The duct section also moves helped maintain good housekeeping at this forward and backwards as previously, pivoted floor area. at the end box connection to a short section Previously without any exhaust, the stair of heavy corrugated rubber tubing which well and elevator shaft were always filled flexes at its lower box connection while the with asbestos and cotton fuzz. The stack ef upper section connects to an inverted Y. Each fect through these areas carried the dispersed leg of this connection is 3 inches in diameter dust from the looms to the rough concrete leading to a 5-inch diameter line entering a cyclone collector located within the plant. Air discharge is to the outdoors. This ar surfaces of the walls and stairs. Now, due to the air demand by the nine looms, the stair wells and elevator shaft are clean. rangement has been successful and dust dis persion has been considerably reduced. Operators in this plant still wear non-ap- Summary proved cotton-type respirators. This presentation covers experiences in six Figures 6a, 6b and 6c illustrate a control asbestos textile plants during the past twenty- developed for a broadcloth weaving loom. five years. Two important and moderately The basis of the design is the enclosure over involved dust control problems are discussed the top of the entire loom area where the for carding units and dry weaving looms. In maximum dust dispersion results, the heddle variably, permission has not been granted to frame and shuttle areas. The simplicity of obtain photographs or to evaluate engineer this design does not indicate that it was ing performance of installed asbestos dust readily acceptable. Asbestos dust dispersion control installations. Information covering has been studied in six asbestos textile plants some modem technical advances in asbestos during the past twenty-five years. Dust con dust control have been provided through the trol has been discussed for many years, with courtesy' of the Asbestos Textile Institute.